Destructive periodontitis lesions are determined by the nature of the lymphocytic response

Altered phenotype and function of dendritic cells in individuals with chronic periodontitis

OBJECTIVE

To investigate the effects of periodontal bacterial lysates on maturation and function of mature monocyte-derived dendritic cells (m-MDDCs) derived from individuals with chronic periodontitis (CP) or healthy periodontal tissue (HP).

DESIGN

m-MDDCs derived from peripheral blood monocytes, cultured for 7 days in presence of interleukin (IL)-4 and granulocyte-macrophage colony stimulating factor (GM-CSF), were stimulated with lysates of Streptococcus sanguinis, Prevotella intermedia, Porphyromonas gingivalis, or Treponema denticola on day 4, and were then phenotyped. IL-10, IL-12 and IFN-gamma concentration in the supernatant of cultures were measured.

RESULTS

Expression of HLA-DR was lower in bacterial-unstimulated mature m-MDDC from CP compared to HP (p=0.04), while expression of CD1a and CD123 were higher in CP. The expression pattern of HLA-DR, CD11c, CD123, and CD1a did not change on bacterial stimulation, regardless of the bacteria. Stimulation with P. intermedia upregulated CD80 and CD86 in CP cells (p≤0.05). Production of IL-12p70 by bacterial-unstimulated m-MDDCs was 5.8-fold greater in CP compared to HP. Bacterial stimulation further increased IL-12p70 production while decreasing IL-10. Significantly more IFN-gamma was produced in co-cultures of CP m-MDDCs than with HP m-MDDCs when cells were stimulated with P. intermedia (p=0.009).

CONCLUSIONS

Bacterial-unstimulated m-MDDC from CP exhibited a more immature phenotype but a cytokine profile biased towards proinflammatory response; this pattern was maintained/exacerbated after bacterial stimulation. P. intermedia upregulated co-stimulatory molecules and IFN-gamma expression in CP m-MDDC. These events might contribute to periodontitis pathogenesis.

Wound biofilms: lessons learned from oral biofilms

Biofilms play an important role in the development and pathogenesis of many chronic infections. Oral biofilms, more commonly known as dental plaque, are a primary cause of oral diseases including caries, gingivitis, and periodontitis. Oral biofilms are commonly studied as model biofilm systems as they are easily accessible; thus, biofilm research in oral diseases is advanced with details of biofilm formation and bacterial interactions being well elucidated. In contrast, wound research has relatively recently directed attention to the role biofilms have in chronic wounds. This review discusses the biofilms in periodontal disease and chronic wounds with comparisons focusing on biofilm detection, biofilm formation, the immune response to biofilms, bacterial interaction, and quorum sensing. Current treatment modalities used by both fields and future therapies are also discussed.

A bacterial glycan core linked to surface (S)-layer proteins modulates host immunity through Th17 suppression

Tannerella forsythia is a pathogen implicated in periodontitis, an inflammatory disease of the tooth-supporting tissues often leading to tooth loss. This key periodontal pathogen is decorated with a unique glycan core O-glycosidically linked to the bacterium's proteinaceous surface (S)-layer lattice and other glycoproteins. Herein, we show that the terminal motif of this glycan core acts to modulate dendritic cell effector functions to suppress T-helper (Th)17 responses. In contrast to the wild-type bacterial strain, infection with a mutant strain lacking the complete S-layer glycan core induced robust Th17 and reduced periodontal bone loss in mice. Our findings demonstrate that surface glycosylation of this pathogen may act to ensure its persistence in the host likely through suppression of Th17 responses. In addition, our data suggest that the bacterium then induces the Toll-like receptor 2-Th2 inflammatory axis that has previously been shown to cause bone destruction. Our study provides a biological basis for pathogenesis and opens opportunities in exploiting bacterial glycans as therapeutic targets against periodontitis and a range of other infectious diseases.

Periodontal diseases in children and adolescents: a clinician's perspective part

Contrasting forms of periodontal disease can affect children and adolescents with varying prevalence, severity and extent, leading to a diverse prognosis in these age groups. For an early diagnosis and treatment of periodontal conditions in young patients, it is essential for the dental practitioner to be able to identify and classify the disease correctly at the earliest opportunity, applying basic principles along with understanding of aetiology and risk factors. The first part of this article discusses the classification, plaque-induced and non-plaque-induced gingival diseases, localized and generalized forms of chronic, as well as aggressive, periodontitis.

CLINICAL RELEVANCE

Knowledge of different forms of periodontal diseases affecting children and adolescents may help to distinguish between different forms of diseases and have value in screening and early diagnosis of the disease.

Aggressive periodontitis defined by recursive partitioning analysis of immunologic factors

BACKGROUND

The present study aims to extend recent findings of a non-linear model of the progression of periodontitis supporting the notion that aggressive periodontitis (AgP) and chronic periodontitis (CP) are distinct clinical entities. This approach is based on the implementation of recursive partitioning analysis (RPA) to evaluate a series of immunologic parameters acting as predictors of AgP and CP.

METHODS

RPA was applied to three population samples, that were retrieved from previous studies, using 17 immunologic parameters. The mean values of the parameters in control subjects were used as the cut-off points. Leave-one-out cross-validation (LOOCV) prediction errors were estimated in the proposed models, as well as the Kullback-Leibler divergence (DKL) of the distribution of positive results in AgP compared to CP and negative results in CP compared to AgP.

RESULTS

Seven classification trees were derived showing that the relationship of interleukin (IL)-4, IL-1, IL-2 has the highest potential to rule out or rule in AgP. On the other hand, immunoglobulin (Ig)A, IgM used to rule out AgP and cluster of differentiation 4 (CD4)/CD8, CD20 used to rule in AgP showed the least LOOCV cost. Penalizing DKL with LOOCV cost promotes the IL-4, IL-1, IL-2 model for ruling out AgP, whereas the single CD4/CD8 ratio with a lowered discrimination cut-off point was used to rule in AgP.

CONCLUSIONS

Although a test is unlikely to have both high sensitivity and high specificity, the use of immunologic parameters in the right model can efficiently complement a clinical examination for ruling out or ruling in AgP.

Host-bacteria crosstalk at the dentogingival junction

The dentogingival junction is of crucial importance in periodontal host defense both structurally and functionally. Oral bacteria exert a constant challenge to the host cells and tissues at the dentogingival junction. The host response is set up to eliminate the pathogens by the innate and adaptive defense mechanisms. In health, the commensal bacteria and the host defense mechanisms are in a dynamic steady state. During periodontal disease progression, the dental bacterial plaque, junctional epithelium (JE), inflammatory cells, connective tissue, and bone all go through a series of changes. The tissue homeostasis is turned into tissue destruction and progression of periodontitis. The classical study of Slots showed that in the bacterial plaque, the most remarkable change is the shift from gram-positive aerobic and facultatively anaerobic flora to a predominantly gram-negative and anaerobic flora. This has been later confirmed by several other studies. Furthermore, not only the shift of the bacterial flora to a more pathogenic one, but also bacterial growth as a biofilm on the tooth surface, allows the bacteria to communicate with each other and exert their virulence aimed at favoring their growth. This paper focuses on host-bacteria crosstalk at the dentogingival junction and the models studying it in vitro.

The K1K2 region of Lys-gingipain of Porphyromonas gingivalis blocks induction of HLA expression by gamma interferon

In the context of periodontal disease, cysteine proteinases or gingipains from Porphyromonas gingivalis have been implicated in the hydrolysis of cytokines, including gamma interferon (IFN-γ). This cytokine plays a crucial role in host defenses, in part, by regulating expression of major histocompatibility complex molecules. Our recent analysis has identified three structurally defined modules, K1, K2, and K3, of the hemagglutinin region of the lysine gingipain Kgp. These three structurally homologous domains have a common β-sandwich topology that is similar to that found in a superfamily of adhesins and carbohydrate binding domains. The three Kgp hemagglutinin modules are distinguished by variation in some of the loops projecting from the β-sandwich core. Recombinant products corresponding to both single and multidomain regions as well as native Kgp bound IFN-γ with similar affinities. Among the adhesin domain constructs, only the K1K2 polypeptide inhibited the upregulation of HLA-1 expression in a human erythroleukemia (K562) line induced by both recombinant and native IFN-γ. The K1K2 polypeptide also inhibited HLA-DR expression induced by IFN-γ in human umbilical vein endothelial cells. These effects were competitively inhibited by coincubation with sodium or potassium chloride solution. The N-terminal residues of IFN-γ were implicated in mediating the effect of K1K2, while antibody binding to loop 1 of K2 blocked the action of K1K2. The findings indicate the potential significance of structurally defined Kgp adhesin modules in the inactivation of IFN-γ but also the potential of K1K2 in locating the target for the catalytic domain of Kgp.

Human periodontal ligament cells facilitate leukocyte recruitment and are influenced in their immunomodulatory function by Th17 cytokine release

The objective of this in vitro study was to examine the immunomodulatory impact of human periodontal ligament (PDL) cells on the nature and magnitude of the leukocyte infiltrate in periodontal inflammation, particularly with regard to Th17 cells. PDL cells were challenged with pro-inflammatory cytokines (IL-1ß, IL-17A, and IFN-γ) and analyzed for the expression of cytokines involved in periodontal immunoinflammatory processes (IL-6, MIP-3 alpha, IL-23A, TGFß1, IDO, and CD274). In order to further investigate a direct involvement of PDL cells in leukocyte function, co-culture experiments were conducted. The expression of the immunomodulatory cytokines studied was significantly increased under pro-inflammatory conditions in PDL cells. Although PDL cells did not stimulate leukocyte proliferation or Th17 differentiation, these cells induced the recruitment of leukocytes. The results of our study suggest that PDL cells might be involved in chronic inflammatory mechanisms in periodontal tissues and thus in the transition to an adaptive immune response in periodontitis.

Bone remodeling-associated salivary biomarker MIP-1α distinguishes periodontal disease from health

BACKGROUND AND OBJECTIVE

The field of salivary diagnostics lacks an accepted and validated biomarker of alveolar bone remodeling. To address this, we examined levels of salivary biomolecules specifically associated with biological aspects of bone remodeling in subjects with chronic periodontitis in a case-control study.

MATERIAL AND METHODS

Levels of macrophage inflammatory protein-1α (MIP-1α), osteoprotegerin, C-telopeptide pyridinoline cross-links of type I collagen and β-C-terminal type I collagen telopeptide in unstimulated whole saliva of 80 subjects (40 subjects with moderate to severe chronic periodontitis and 40 sex- and age-matched healthy control subjects) were measured using enzyme immunosorbent assays. Saliva was collected before clinical examination, which included probing depth, clinical attachment loss and bleeding on probing.

RESULTS

The mean level of MIP-1α in subjects with periodontitis was 18-fold higher than in healthy subjects (p < 0.0001). Clinical periodontal indices correlated significantly with MIP-1α levels (p < 0.0001). Of the biomolecules examined, MIP-1α demonstrated the greatest ability to discriminate between periodontal disease and health as determined by the area under the curve (0.94) and classification and regression tree analysis (sensitivity 94% and specificity 92.7%). Osteoprotegerin levels were elevated 1.6-fold (p = 0.055), whereas C-telopeptide pyridinoline cross-links of type I collagen and β-C-terminal type I collagen telopeptide levels were below the level of detection in the majority of subjects.

CONCLUSION

These findings suggest that the chemokine MIP-1α may aid in identifying periodontitis. Future longitudinal studies are warranted to determine whether this biomarker can help in ascertaining the progression of bone loss in subjects with periodontal disease.

T-helper cells in the etiopathogenesis of periodontal disease: A mini review

Our traditional understanding of the T-helper (Th)1/Th2 paradigm in periodontal disease has undergone considerable changes in recent years. This review focuses on the Th subsets, including the recently identified cells of the CD4 lineage, their activation pathways and effector function in periodontal disease. The roles of Th17 and regulatory T (Treg) cells in disease pathogenesis have been explored. Newer Th subsets such as Th9 and Th22 cells and their potential role in periodontal disease have also been outlined.

TLR2 signaling and Th2 responses drive Tannerella forsythia-induced periodontal bone loss

Periodontal disease (PD) is a chronic inflammation of the tooth-supporting soft tissue and alveolar bone due to infection by a select group of gram-negative microbes, which leads to tooth loss if untreated. Because mice deficient in CD4(+) cells are resistant to infection-induced alveolar bone loss, Th cells have been implicated in bone-destructive processes during PD. However, the extent to which different Th cell subtypes play roles in pathogenesis or host protection remains to be defined and is likely to vary depending on the dominant microorganism involved. By far, Porphyromonas gingivalis is the best-studied periodontal microbe in PD. Although the gram-negative anaerobe Tannerella forsythia is also a vital contributor to periodontal bone loss, almost nothing is known about immune responses to this organism. Previous studies from our laboratory revealed that T. forsythia induces periodontal bone loss in mice and that this bone loss depends on the bacterially expressed BspA protein. In this study, we showed that T. forsythia activates murine APCs primarily through TLR2-dependent signaling via BspA. Furthermore, T. forsythia infection causes a pronounced Th2 bias, evidenced by T cell expression of IL-5, but not IFN-γ or IL-17, in draining lymph nodes. Consistently, deficiencies in TLR2 or STAT6 result in resistance to T. forsythia-induced alveolar bone loss. Thus, TLR2 signaling and Th2 cells play pathogenic roles in T. forsythia-induced alveolar bone destruction.

How is the development of dental biofilms influenced by the host?

BACKGROUND

The host provides environmental conditions that support diverse communities of microorganisms on all environmentally-exposed surfaces of the body.

MATERIALS AND METHODS

To review the literature to determine which properties of the host substantially influence the development of dental biofilms.

RESULTS

The mouth facilitates the growth of a characteristic resident microbiota. The composition of the oral microbiota is influenced by temperature, pH, and atmosphere, as well as by the host defences and host genetics. In addition, the host supplies endogenous nutrients and a variety of surfaces for biofilm formation. In health, the resident oral microbiota forms a symbiotic relationship with the host, regulated by active host-microbe cross talk. This resident microbiota is sensitive to perturbations in the host environment, especially to changes in nutrient supply and pH, so that previously minor components of the microbiota can become more competitive (and vice versa), resulting in reorganization of biofilm community structure.

CONCLUSION

The host environment dictates the composition and gene expression of the resident microbiota. Changes in oral environmental conditions can disrupt the normal symbiotic relationship between the host and its resident microbes, and increase the risk of disease.

Interferon-gamma promoter hypomethylation and increased expression in chronic periodontitis

AIM

The goal of this investigation was to determine whether epigenetic modifications in the IFNG promoter are associated with an increase of IFNG transcription in different stages of periodontal diseases.

MATERIALS AND METHODS

DNA was extracted from gingival biopsy samples collected from 47 total sites from 47 different subjects: 23 periodontally healthy sites, 12 experimentally induced gingivitis sites and 12 chronic periodontitis sites. Levels of DNA methylation within the IFNG promoter containing six CpG dinucleotides were determined using pyrosequencing technology. Interferon gamma mRNA expression was analysed by quantitative polymerase chain reactions using isolated RNA from part of the biological samples mentioned above.

RESULTS

The methylation level of all six analysed CpG sites within the IFNG promoter region in the periodontitis biopsies {52% [interquartile range, IQR (43.8%, 63%)]} was significantly lower than periodontally healthy samples {62% [IQR (51.3%, 74%)], p=0.007} and gingivitis biopsies {63% [IQR (55%, 74%)], p=0.02}. The transcriptional level of IFNG in periodontitis biopsies was 1.96-fold and significantly higher than tissues with periodontal health (p=0.04). Although the mRNA level from experimental gingivitis samples exhibited an 8.5-fold increase as compared with periodontally healthy samples, no significant methylation difference was observed in experimental gingivitis sample.

CONCLUSIONS

A hypomethylation profile within IFNG promoter region is related to an increase of IFNG transcription present in the chronic periodontitis biopsies, while such an increase of IFNG in experimentally induced gingivitis seems independent of promoter methylation alteration.

Autoimmune responses in periodontal diseases

Periodontal diseases are characterized by localized infections and inflammatory conditions and directly affect teeth supporting structures which are the major cause of tooth loss. Several studies have demonstrated the involvement of autoimmune responses in periodontal disease. Evidences of involvement of immunopathology have been reported in periodontal disease. Bacteria in the dental plaque induce antibody formation. Lymphocytes, cytokines and complement system are reported to have an important role in the progression of periodontal disease. The present review describes the involvement of autoimmune responses in periodontal diseases. The mechanisms underlying these responses are also discussed.

Cardiovascular disease and the role of oral bacteria

In terms of the pathogenesis of cardiovascular disease (CVD) the focus has traditionally been on dyslipidemia. Over the decades our understanding of the pathogenesis of CVD has increased, and infections, including those caused by oral bacteria, are more likely involved in CVD progression than previously thought. While many studies have now shown an association between periodontal disease and CVD, the mechanisms underpinning this relationship remain unclear. This review gives a brief overview of the host-bacterial interactions in periodontal disease and virulence factors of oral bacteria before discussing the proposed mechanisms by which oral bacterial may facilitate the progression of CVD.

Sex differences in destructive periodontal disease: exploring the biologic basis

BACKGROUND

Epidemiologic studies provide broad-based evidence that men are at greater risk for developing destructive periodontal disease than women, even after adjusting for behavioral and environmental factors, such as oral hygiene practice and smoking. What requires clarification, however, is whether sex-specific differences in immune function provide a plausible biologic basis for a sexual dimorphism in susceptibility to destructive periodontal disease. This review examines evidence that might provide an underlying biologic basis for a sexual dimorphism in the prevalence and severity of destructive periodontal disease.

METHODS

A narrative review of the literature related to sexual dimorphism in pathogen-mediated inflammatory diseases and immune response was retrieved from searches of computerized databases (MEDLINE, PubMed, and SCOPUS).

RESULTS

Sex steroids exert profound effects on multiple immunologic parameters regulating both the amplification and resolution of inflammation. Strong evidence exists for sexual dimorphisms in immune function, involving both innate and acquired immunity. Injury and infection have been associated with higher levels of inflammatory cytokines, including interleukin-1β and tumor necrosis factor-α, in men than women, paralleling observed sex-specific differences in periodontitis.

CONCLUSION

Differential gene regulation, particularly in sex steroid-responsive genes, may contribute to a sexual dimorphism in susceptibility to destructive periodontal disease.

Transcriptional regulation of the mucosal immune system mediated by T-bet

The immune system faces the arduous task of defending the mucosal surfaces from invading pathogens, but must simultaneously repress responses against commensal organisms and other inert antigens that are abundant in the external environment, as inappropriate immune activation might expose the host to increased risk of autoimmunity. The behavior of individual immune cells is governed by the expression of transcription factors that are responsible for switching immune response genes on and off. T-bet (T-box expressed in T cells) has emerged as one of the key transcription factors responsible for controlling the fate of both innate and adaptive immune cells, and its expression in different immune cells found at mucosal surfaces is capable of dictating the critical balance between permitting robust host immunity and limiting susceptibility to autoimmunity and allergy.

Destructive and protective roles of cytokines in periodontitis: a re-appraisal from host defense and tissue destruction viewpoints

Periodontal diseases (PD) are chronic infectious inflammatory diseases characterized by the destruction of tooth-supporting structures, being the presence of periodontopathogens required, but not sufficient, for disease development. As a general rule, host inflammatory mediators have been associated with tissue destruction, while anti-inflammatory mediators counteract and attenuate disease progression. With the discovery of several T-cell subsets bearing distinct immunoregulatory properties, this pro- vs. anti-inflammatory scenario became more complex, and a series of studies has hypothesized protective or destructive roles for Th1, Th2, Th17, and Treg subpopulations of polarized lymphocytes. Interestingly, the "protective vs. destructive" archetype is usually considered in a framework related to tissue destruction and disease progression. However, it is important to remember that periodontal diseases are infectious inflammatory conditions, and recent studies have demonstrated that cytokines (TNF-α and IFN-γ) considered harmful in the context of tissue destruction play important roles in the control of periodontal infection. Therefore, in this review, the state-of-the-art knowledge concerning the protective and destructive roles of host inflammatory immune response will be critically evaluated and discussed from the tissue destruction and control-of-infection viewpoints.

In vitro cytokine responses to periodontal pathogens: generalized aggressive periodontitis is associated with increased IL-6 response to Porphyromonas gingivalis

Generalized aggressive periodontitis (GAgP) is an inflammatory condition resulting in destruction of tooth-supporting tissues. We examined the production of IL-1beta, IL-6, tumour necrosis factor (TNF)-alpha, IL-12 and IL-10 in cultures of peripheral mononuclear cells (MNC) from 10 patients with GAgP and 10 controls stimulated with periodontal pathogens or a control antigen, tetanus toxoid (TT) in the presence of autologous serum. The pathogens used were Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum, either as type strains or bacteria isolated from the participants' inherent oral flora. The P. gingivalis -induced production of IL-6 was approximately 2.5-fold higher in patients with GAgP than in healthy controls (P < 0.05), while the corresponding TNF-alpha production was non-significantly elevated. IL-1beta production induced by P. gingivalis, as all cytokine responses induced by Pr. intermedia, F. nucleatum and TT was similar in the two groups. A reduced IL-12p70 response to Pr. intermedia and F. nucleatum was observed in smokers compared to non-smoking patients (P < 0.02). To assess the role of serum factors in the elevated IL-6 response to P. gingivalis, MNC from two donors free of disease were stimulated with this bacterium in the presence of the various patient and control sera. An elevated IL-6 and TNF-alpha response was observed in the presence of patient sera (P < 0.01 and P < 0.04, respectively). The data suggest that an exaggerated production of IL-6 occurs in GAgP, and that pro-inflammatory serum factors play an essential role in the response.

Association of periodontitis with rheumatoid arthritis and atherosclerosis: Novel paradigms in etiopathogeneses and management?

There is increasing documentation of a link between inflammatory periodontal disease affecting the supporting structure of teeth, rheumatoid arthritis, and coronary artery disease. Periodontitis is initiated predominantly by Gram-negative bacteria and progresses as a consequence of the host inflammatory response to periodontal pathogens. Lipopolysaccharide, a cell wall constituent stimulates the production of inflammatory cytokines via the activation of signaling pathways perpetuating inflammatory pathogenesis in a cyclical manner in susceptible individuals; with an element of autoimmune stimulation, not dissimilar to the sequential events seen in RA. Periodontitis, also implicated as a risk factor for cardiovascular disease, promotes mechanisms for atherosclerosis by enhancing an imbalance in systemic inflammatory mediators; more direct mechanisms attributed to microbial products are also implicated in both RA and atherogenesis. Severe periodontal disease characterized by clinical and radiographic parameters has been associated with ischemic stroke risk, significant levels of C-reactive protein and serum amyloid A, amongst others common to both periodontitis and atherosclerosis. Existing data supports the hypothesis that persistent localized infection in periodontitis may influence systemic levels of inflammatory markers and pose a risk for RA and atherosclerosis. A common nucleus of activity in their pathogeneses provides novel paradigms of therapeutic targeting for reciprocal benefit.

FAM5C contributes to aggressive periodontitis

Aggressive periodontitis is characterized by a rapid and severe periodontal destruction in young systemically healthy subjects. A greater prevalence is reported in Africans and African descendent groups than in Caucasians and Hispanics. We first fine mapped the interval 1q24.2 to 1q31.3 suggested as containing an aggressive periodontitis locus. Three hundred and eighty-nine subjects from 55 pedigrees were studied. Saliva samples were collected from all subjects, and DNA was extracted. Twenty-one single nucleotide polymorphisms were selected and analyzed by standard polymerase chain reaction using TaqMan chemistry. Non-parametric linkage and transmission distortion analyses were performed. Although linkage results were negative, statistically significant association between two markers, rs1935881 and rs1342913, in the FAM5C gene and aggressive periodontitis (p = 0.03) was found. Haplotype analysis showed an association between aggressive periodontitis and the haplotype A-G (rs1935881-rs1342913; p = 0.009). Sequence analysis of FAM5C coding regions did not disclose any mutations, but two variants in conserved intronic regions of FAM5C, rs57694932 and rs10494634, were found. However, these two variants are not associated with aggressive periodontitis. Secondly, we investigated the pattern of FAM5C expression in aggressive periodontitis lesions and its possible correlations with inflammatory/immunological factors and pathogens commonly associated with periodontal diseases. FAM5C mRNA expression was significantly higher in diseased versus healthy sites, and was found to be correlated to the IL-1β, IL-17A, IL-4 and RANKL mRNA levels. No correlations were found between FAM5C levels and the presence and load of red complex periodontopathogens or Aggregatibacter actinomycetemcomitans. This study provides evidence that FAM5C contributes to aggressive periodontitis.

Th17 cytokines in mucosal immunity and inflammation

PURPOSE OF REVIEW

Compelling evidence suggests that the Th17 lineage and other IL-17-producing cells play critical roles in host defense against pathogens at mucosal sites. However, IL-17 can also contribute to inflammatory responses at mucosal sites. In this review, we will discuss the recent progress in our understanding of the role of Th17 and other IL-17-producing cells in defining the fine balance between immunity and inflammation at different mucosal sites. RECENT FNDINGS: Recent findings have highlighted that Th17 cytokines are important for the induction of innate and adaptive host responses and contribute to host defense against pathogens at mucosal sites. More recent developments have probed how the Th17 responses are generated in vivo in response to infections and their requirement in maintaining barrier function at mucosal sites. Most importantly, it is becoming apparent that there is a fine balance between protective and pathological manifestation of Th17 responses at mucosal sites that defines immunity or inflammation.

SUMMARY

In this review, we have summarized the recent advances in our understanding of Th17 cytokines and how they contribute to immunity versus inflammation at mucosal sites.

Lymphocyte subpopulation in healthy and diseased gingival tissue

In this study, infiltrating lymphocytes subpopulation in gingival sections of healthy, inflamed, and periodontitis lesions was investigated. A set of cluster of differentiation (CD) antigen specific monoclonal/polyclonal antibodies to detect different cell types within the tissues was used. These included anti-CD3 (pan T-cell), anti-CD45RO (memory T-cell), anti-CD20 (B-cell), and kappa light chain (plasma cells). Biopsies of gingival tissue were obtained from 17 patients who had clinically healthy gingiva, from 18 patients with gingivitis, and 17 patients with periodontitis.

A significantly greater proportion of T-cells (P < 0.00) was observed in healthy gingival and gingivitis tissue samples compared to periodontitis tissue samples. In addition, a greater proportion of B-cells was observed in periodontitis lesions than in the gingival lesions (P < 0.00). The memory T-cells and the kappa light-chain plasma cells were present in both healthy and diseased tissues, suggestive of previous activation by periodontal pathogenic microorganisms.

In conclusion, these differences in the relative proportions of B- and T-cells may reflect a difference in the immunopathology of periodontitis and gingivitis lesions.

The interleukin-4 -34TT and -590TT genotype is correlated with increased expression and protein production in aggressive periodontitis

Aggressive periodontitis (AgP) is a severe periodontal disease characterized by rapid destruction of the tissues supporting the teeth in otherwise healthy individuals. The frequency of the interleukin-4 homozygous -34TT and -590TT genotype was increased in patients in comparison with controls. This study aimed to test the functional effect of this specific genotype in AgP patients by analyzing gene expression of IL-4 and STAT6, and protein concentration of IL-4, in activated CD4+ T cells. Results revealed an increased IL-4 and STAT6 expression and IL-4 production in the cells of the patients who were homozygous for the -34T and -590T alleles in comparison with the patients who were homozygous for the -34C and -590C alleles (p<0.05). These findings demonstrate that the IL-4 -34TT and -590TT genotype has a functional effect on T helper (Th) cells of patients with AgP, inducing increased expression of IL-4 and STAT6, and increased production of IL-4.

Histologic and histomorphometric features of bisphosphonate-related osteonecrosis of the jaws: an analysis of 31 cases with confocal laser scanning microscopy

INTRODUCTION

Patients undergoing bisphosphonate therapies may develop jaw lesions, mainly consisting in bone necrosis. No effective treatment has been proposed so far for such lesions, nor is there a uniform concept on the possible pathogenesis of this entity.

METHODS

The study population included 31 patients with bisphosphonate-related osteonecrosis of the jaws and 10 healthy donors. All patients underwent to jaw bone biopsy and the tissue samples were divided into two parts, one of which was fixed, decalcified and routinely processed. The second part was fixed, embedded in methylmetacrylate, cut and stained with methylene blue and basic fuchsine. All samples were subjected to light and confocal microscopic examination and to histomorphometric analyses to evaluate differences in bone structure between the two samples groups.

RESULTS

Three main histological patterns were identified in ONJ patients: 1 - Areas with active acute inflammation, characterized by predominance of soft tissues, inflammatory infiltrate, acellular necrotic debris, thin-walled and dilated blood vessel, intensely basophilic bone spiculae with scalloped borders showing prominent bone resorption. 2 - Areas characterized by predominance of bony structures showing wide acellular necrotic sequestra and large, scalloped Haversian canals containing inflammatory cells. 3 - Non-necrotic areas contained larger amounts of bone, showing increased trabecular thickness, inter-osteonic bone deposition and smaller and fewer Haversian canals. These differences were more evident after comparing the histomorphometrical data of samples from ONJ patients with controls. Also, lamellar bone from treated patients was composed of bigger osteones containing larger osteocytes. Two different types of newly-formed woven bone, mainly showing centrifugal spatial orientation, were easily detectable in these areas. Osteoclast-like cells detected in inflammatory areas from treated patients were small and contained few nuclei, but they were rare to absent in non-necrotic bone from the same patients.

CONCLUSIONS

These features point at a peculiar process of bone remodeling in patients undergoing bisphosphonate therapy, which showed scarce osteoclastic activity and subsequent deposition of newly-formed bone. The latter would be made up of thicker bone structures supplied by fewer blood vessels. Consequently, in case of increased metabolic requests, this modified bone would not be supported by adequate blood supply, thus leading to necrosis and superinfection.

Decreased interleukin-2 responses to Fusobacterium nucleatum and Porphyromonas gingivalis in generalized aggressive periodontitis

BACKGROUND

Compromised T-cell responses to periodontal pathogens may contribute to the pathogenesis of generalized aggressive periodontitis (GAgP). In this study, we attempted to characterize T-helper cell (Th1, Th2, and Th17) responses in patients with GAgP and healthy controls upon stimulation with disease-relevant pathogens.

METHODS

Mononuclear cells (MNCs) from 10 white patients with GAgP and 10 white controls were stimulated with Porphyromonas gingivalis American Type Culture Collection (ATCC) 33277 (Pg), Prevotella intermedia ATCC 25611, Fusobacterium nucleatum ATCC 49256 (Fn), and similar bacteria isolated from the participants' inherent oral flora. Tetanus toxoid (TT) was used as control antigen. The resulting production of interferon-gamma (IFN-gamma) and interleukin (IL)-2, -4, -5 and -17 and the induced proliferation of CD4+ T cells were measured.

RESULTS

MNCs from patients with GAgP exhibited decreased IL-2 responses to Pg and Fn. No difference was observed between patients with GAgP and controls with regard to CD4+ T-cell proliferation or the production of IFN-gamma and IL-4, -5, and -17, irrespective of whether type strains or bacteria isolated from the participants' oral cavity were used for stimulation. Moreover, similar proliferative and cytokine responses to TT were observed. Notably, smoking patients with GAgP exhibited significantly lower IFN-gamma responses to the bacteria and to TT than non-smoking patients or controls.

CONCLUSIONS

The decreased IL-2 responses of patients with GAgP to Pg and Fn combined with adequate IL-2 responses to TT suggest an impaired antigen-specific T-cell reactivity with periodontal pathogens in GAgP. The decreased IFN-gamma responses of smokers within the patient group suggest that smoking may aggravate this impairment.

Relations Between Serum IgA Level and Cartilage Erosion in 436 Cases of Rheumatoid Arthritis

The objective of this work was to explore the correlation between the cartilage erosion tested with X-ray image and the serum immune globulin level in rheumatoid arthritis (RA). Four hundred and thirty-six patients with active RA in preliminary diagnosis were selected for the study. The cartilage erosion was measured by X ray in both hands as a grade index, and IgG, IgM as well as IgA in serum were determined with immunoturbidimetry. The correlation between the X-ray grading and serum immune globulin outcomes was analyzed by SPSS13.0 statistic package.

RESULT

More patients with X-ray grading as cartilage erosion (slight, medium or severe) showed abnormal IgA comparing to those in X-ray grading as normal (p<0.05-0.01) both in preliminary investigation and after 6 months' follow-up. The serum IgA level in RA with X-ray grading as slight, medium or severe cartilage erosion was elevated remarkably comparing with in grading as normal (p<0.05-0.01). The Spearman Analysis showed that the level of serum IgA presents positive correlation with X-ray grading both in preliminary investigation (p=0.003, rIgA=0.143) and after 6 months follow-up (p=0.001, rIgA=0.173). IgG and IgM, however, have no correlation with X-ray image outcomes. The increase of serum IgA shows positive correlation with the grade of cartilage damage in active RA. IgA seems to be involved in the mechanism of joint cartilage erosion in active RA.

Neutrophils rescue gingival epithelial cells from bacterial-induced apoptosis

In the pathogenesis of chronic inflammatory periodontal disease, neutrophils are recognized as a major cellular component from the histopathology of the periodontal lesion around teeth and from clinical cases where absence or dysfunction of neutrophils results in major periodontal destruction. Neutrophils are recruited in vast numbers into the gingival crevice during periodontal inflammation, attracted by microbial plaque chemoattractants and chemokines released following microbial perturbation of gingival epithelial cells. Porphyromonas gingivalis, a major periodontopathogen, triggers a vast array of cellular responses in gingival epithelial cells but also induces apoptosis. We demonstrate here that neutrophils, when combined in a P. gingivalis challenge assay of epithelial cells, prevent epithelial cell apoptosis by phagocytosing P. gingivalis and later undergoing apoptosis themselves. By removing P. gingivalis by phagocytosis, neutrophils also protect the host from the harmful effects of its microbial proteases, which degrade inflammatory cytokines and other host molecules.